Optical networks using WDM (Wavelength Division Multiplexing) are now proposed to be built more and more. In such networks a plurality of add/drop nodes are connected and simple devices should be provided for connecting the nodes to the network. For example, when an existing node is expanded to be capable of receiving and transmitting in another wavelength band the manual work required therefor should be minimized. An optical network having add/drop nodes is for example disclosed in U.S. Pat. No. 5,754,545.